V8: avoid deadlock when profiling is active

A deadlock happens when sampler initiated by SIGPROF tries to lock
the thread and the thread is already locked by the same thread. As
a result, other thread involved in sampling process hangs. The
patch adds a check for thread lock before continuing sampler
operation.

The fix has been tested on a sample app under load with and without
profiling turned on.

Fixes issue #14576 and specifically the duplicate issue #25295

Reviewed-By: Julien Gilli <julien.gilli@joyent.com>
PR-URL: #25309

deps/v8/src/isolate.h

@@ -384,6 +384,11 @@ class Isolate {
  public:
   ~Isolate();
 
+  // ISSUE-14576: allow to access process_wide_mutex_ from sampler.cc
+  static base::Mutex* GetProcessWideMutexPointer() {
+    return process_wide_mutex_.Pointer();
+  }
+
   // A thread has a PerIsolateThreadData instance for each isolate that it has
   // entered. That instance is allocated when the isolate is initially entered
   // and reused on subsequent entries.

deps/v8/src/sampler.cc

@@ -342,6 +342,14 @@ void SignalHandler::HandleProfilerSignal(int signal, siginfo_t* info,
     // We require a fully initialized and entered isolate.
     return;
   }
+
+  // ISSUE-14576: To avoid deadlock, return if there is a thread lock
+  if (Isolate::GetProcessWideMutexPointer()->TryLock()) {
+    Isolate::GetProcessWideMutexPointer()->Unlock();
+  } else {
+    return;
+  }
+
   if (v8::Locker::IsActive() &&
       !isolate->thread_manager()->IsLockedByCurrentThread()) {
     return;

test/simple/test-regress-GH-14576.js

@@ -0,0 +1,57 @@
+// Copyright Joyent, Inc. and other Node contributors.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to permit
+// persons to whom the Software is furnished to do so, subject to the
+// following conditions:
+//
+// The above copyright notice and this permission notice shall be included
+// in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
+// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+// USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+/*
+ * Tests for sampler deadlock regression. 
+ * Issue https://github.com/joyent/node/issues/14576
+ */
+
+var assert = require('assert');
+var cp = require('child_process');
+
+var child = undefined;
+
+if (process.platform !== 'win32') {
+  process.on('SIGTERM', function() {
+    if(child) {
+      process.kill(child.pid, 'SIGKILL');
+    }
+
+    process.exit();
+  });
+}
+
+var testScript = "var i = 0; function r() { if(++i > 25) return; " +
+                 "setTimeout(r, 1); }; r();"
+var nodeCmd = process.execPath + 
+              ' --prof --nologfile_per_isolate' + 
+              ' -e "' + testScript + '"';
+var runs = 0;
+
+function runTestScript() {
+  child = cp.exec(nodeCmd, function(err, stdout, stderr) {
+    if (++runs > 50) return;
+
+    runTestScript();
+  });
+}
+
+runTestScript();